This is for a Java program I'm working on as part of a homework assignment. I don't want the work done for me, but I'm stuck. I'm fairly new to Java, and using NetBeans IDE 7.0.1.

I'm having difficulty with some exception handling when trying to validate user input. This program will log charitable donations from user input. However, I've not been successful in validating the donation amount text field input. If a user inputs text instead of numbers, I would like them to be notified that their input was invalid, and I'd like the exception handling to handle the error and carry on after the user fixes their entry. Any help is greatly appreciated.

Many thanks for the input folks. It seems that it's working from what I can tell. However, I'm having a new issue when I did some user input testing. If I input whole dollar amounts it works, but if I enter 10.00, 100.00, etc... it does not seem to validate. Any thoughts?
–
WilMay 28 '12 at 2:54

Something like this would work. This checks so that the amount is not empty and contains only digits based on your exisiting method.

public boolean donationAmt(String amount) {
if(amount==null || amount=="" || amount.length()<1){ //check so that the amount field is not empty, pherhaps you can add a check so the amound is not 0 :)
JOptionPane.showMessageDialog(null, "Invalid Input. The amount cannot be empty");
return false;
}
for(int i = 0; i < amount.length(); i++){ //loop thru the string and check so that each char is a digit
if (!Character.isDigit(amount.charAt(i))){
JOptionPane.showMessageDialog(null, "The amount can contain only numbers");
return false;
}
return true;

If you want to make sure that the amount is not 0, one approach would be to parse amount to int, and check so that parsedAmount<0. This should be done after it's verified that the amount is not empty and is only digits (e.i last:) ) to avoid NPE's and numberformatexception